https://github.com/google/walt

A device for measuring latency of physical sensors and outputs on phones and computers
https://github.com/google/walt

Last synced: 16 days ago
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A device for measuring latency of physical sensors and outputs on phones and computers

• Host: GitHub
• URL: https://github.com/google/walt
• Owner: google
• License: apache-2.0
• Created: 2016-02-26T19:41:21.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2024-03-13T21:58:13.000Z (8 months ago)
• Last Synced: 2024-08-01T05:20:59.277Z (3 months ago)
• Language: Java
• Homepage:
• Size: 8.03 MB
• Stars: 442
• Watchers: 34
• Forks: 74
• Open Issues: 26
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE
  • Authors: AUTHORS

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README

        
## WALT Latency Timer ##

**DISCLAIMER:** This is not an official Google product.

 * [Post about WALT on Android Developers Blog](http://android-developers.blogspot.ca/2016/04/a-new-method-to-measure-touch-and-audio.html)

 * [Instructional videos showing how to use WALT](https://www.youtube.com/playlist?list=PLd6Fi7WgXfcCEJg1FDqNCoQfpWo7W3J5a)

 * [Detailed usage instructions](docs/usage/WALT_usage.md)

 * Mailing list - [walt-discuss](https://groups.google.com/forum/#!forum/walt-discuss)

 * Low-traffic mailing list for major announcements [walt-announce](https://groups.google.com/forum/#!forum/walt-announce)

WALT is designed to measure the latency of physical sensors and outputs on phones and computers. It can currently perform the following measurements:

 * [Tap latency](docs/TapLatency.md) - time from the moment a finger-like probe touches down (or up) on the screen

   until the kernel timestamps an ACTION_DOWN (or ACTION_UP) event. This physical contact with

   the screen is timed using an accelerometer mounted on the probe.

 * [Drag latency](docs/DragLatency.md) (scroll).

 * [Screen draw latency](docs/ScreenLatency.md) - using a photodiode that detects whether the screen is black or white.

 * [Audio output and microphone latencies](docs/AudioLatency.md).

 * MIDI input and output latencies

The WALT app for Android can be

[installed from Google Play](https://play.google.com/store/apps/details?id=org.kamrik.latency.walt)

or downloaded in the [releases section](https://github.com/google/walt/releases); the iOS app must be built from source.

![WALT photo](docs/WALT_photo_audio_r07.jpg)

## Notes

* Hardware build instructions can be found in this repository under `hardware/`.

* Clock synchronization details are described [here](android/WALT/app/src/main/jni/README.md).

* The Android/iOS device and Teensy clocks have a tendency to diverge due to

  differing clock frequencies. This means they will go out of sync after

  several minutes. The workaround is to use the app to re-sync the

  clocks. Some, but not all tests in the app will sync the clocks when starting a measurement.

* Python code used to communicate with WALT from Linux and ChromeOS can be found

  [here](https://chromium.googlesource.com/chromiumos/platform/touchbot/+/master/quickstep/).